Human powered vehicles, such as bicycles, often have indicators of performance, from a simple speedometer to sophisticated computers which report such data as distance, average and instantaneous speed, and such. Most depend upon simple manipulation of data derived from wheel speed and number of rotations. GPS products have added the notion approximate altitude, location, navigation, even tracking. Some products, such as heart monitors, report performance or status of a human powering the vehicle.
It is also desirable to measure performance indications such as the power produced and the total energy expended. As athlete training continues to be more and more sophisticated, some training is conducted indoors under controlled conditions, where typically large or stationary equipment is used. However many athletes and trainers want to monitor performance in real time under actual conditions. Some products measure pedal torque, power output and energy expended by direct or indirect measurements of the forces that the rider is applying to drive a vehicle forward. Examples include mechanical strain gauges installed in crank mechanisms or wheel hubs to measure the applied forces and speeds, and thus derived indications corresponding to power and energy.
The prior art includes solutions wherein expensive sensors are installed in the crank or rear hub of a bicycle. Many such systems require the user to use a customized crank or hub, which is difficult to install or move to another vehicle, often requiring installation by a trained technician.